1. Field of the Invention
This invention relates to an insulating tape used for producing winding coils which are usually used in electric apparatus such as home electric appliances or in electronic devices used in telecommunication systems or the like.
2. Description of the Related Art
In electric apparatus such as home electric appliances or in electronic devices used in telecommunication systems or the like, the winding coils used as the switching transformers or the like usually have the construction as shown in FIG. 3, with wirings 21 and insulated tape 22 alternately wound on a bobbin 10.
The bobbin 10 has rim portions 12 and 13 provided on both ends of a body portion 11 thereof, as shown in FIG. 4.
One of the rim portions, for example, the rim portion 12, has a plurality of terminal portions 14 projected from a side surface.
These bobbins 10 usually are given a common configuration instead of preparing several kinds of bobbins with different configurations for each winding coil. An insulating layer is usually formed on the body portion 11 of the bobbin 10 by winding narrow, insulating strips on the two side edge portions or one of the side edge portions, depending on the amount of wiring to be wound on the bobbin or the width of the winding in each winding layer.
The manufacturing steps for producing the winding coil explained above illustrated in FIG. 5-A to 5-F.
In these figures, each bobbin 10 is shown schematically. One of the rim portions 12 thereof is omitted from each drawing to make them more understandable.
First, narrow insulating strips 23 having a predetermined width are wound on both side edge portions of the body portion 11 to form ridged portions 23A and 23B, respectively (as shown in FIG. 5-A).
When an end portion of the wiring material 21 is terminated with a predetermined terminal 14, not shown in FIG. 5-B, it is wound on the body portion 11 of the bobbin 10 starting at the edge portion of the ridged portion 23A (as shown in FIG. 5-B).
After a certain amount of the wiring material 21 is wound on the body portion 11 along a longitudinal direction thereof and when the wiring material 21 reaches a position on which an end portion of the other ridged portion 23B exists (as shown in FIG. 5-C), an adhesive is coated over the whole surface of the wiring material 21 just wound on the body portion 11, then a predetermined amount of an insulating tape 22 having the same width as that of the body portion 11 is wound on the adhesive layer.
After that, the wiring material 21 is folded on the surface of the insulating tape 22 toward the terminal 14 (as shown in FIG. 5-D).
When the wiring material 21 is entangled with the terminal 14, a predetermined amount of the insulating tape 22 is wound again on the body portion 11 to cover the wiring material 21 arranged on the previously wound insulating tape 22 (as shown in FIG. 5-E).
When a first wiring layer is formed by the operation as explained above, two narrow insulating strips 23 having a predetermined width are wound on the two end portions of the insulating tape 22 to form ridged portions 23A and 23B (as shown in FIG. 5-F).
Then, the wire winding operation as explained above is again carried out to form a second wiring layer, etc. Finally, a wiring coil is produced provided with a plurality of wiring layers, as shown in FIG. 3.
As explained above, the wiring coil thus produced includes the narrow insulating strips 23 which form the ridged portions 23A and 23B as insulated layers.
However, the narrow insulating strips have extremely small stiffness and strength since they are 0.05 to 1.0 mm in thickness and 2 to 10 mm in width.
Accordingly, when the narrow insulating strips 23 are wound on the bobbin 10 or on a surface of the wiring material 21, the insulating strips 23 are twisted even with a slight tension applied thereto. This makes it difficult for the insulating strips 23 to be wound precisely on a predetermined place.
Also, when tension is applied to the insulating strips 23, they are deformed, for example, are reduced in the thickness or the width, or are broken, to make it difficult to form a predetermined insulating layer.
Therefore, insulating strips having relatively high stiffness and strength should be used. Further, the operator should wind the insulating strips on the bobbin with a great care so as not to apply unnecessary tension thereto.
This causes a problem of extremely low operational efficiency for producing the wiring coils.